A. Field of the Invention
The present invention relates to manipulator apparatus, and more particularly, to manipulator apparatus which may be manually programmed by an operator moving the apparatus through a series of operations to automatically record data derived from encoder signals associated with each axis of the manipulator. The recorded data is read out during a playback mode to control movement of the apparatus. The recording during programming is under the control of a rotating guide apparatus positioned at the manipulator end effector during programming.
B. Description of the Prior Art
Programmed manipulator apparatus utilizing various programming techniques have been developed for work operations such as welding, assembly and repetitive work cycles. While these arrangements have in general, been satisfactory for their intended purpose, they are usually not readily portable because of their substantial weight and hence are usually employed to do repetitive tasks at one location. While some prior art manipulators have been mounted on rails for limited movement, even these arrangements are not suitable for work over large areas such as in the interior welding of ship hulls, longitudinal stiffener supports and bulkheads. In such an environment there is a need for a lightweight, portable manipulator apparatus which can be readily moved to a given area, clamped in position, programmed by manually moving the end of the manipulator arm over a desired welding path in that area, and then operated automatically to make the weld while the operator programs another similar manipulator for welding in an adjacent area. Such portable manipulators can conveniently be supported on the longitudinal stiffener supports of the ship's hull and slid along these longitudinals to different work areas associated with the transverse bulkheads which are to be welded to the longitudinals and the ship bottom. Prior art manipulator apparatus has not been capable of performing such task because of the massive base portions of such apparatus which are necessary when the manipulator arm is used to move heavy articles from one place to another. Furthermore, the drive trains of such prior art apparatus are of such large step-down ratios that it is very difficult if not impossible to move the encoders associated with each axis by driving backward through these drive trains if an attempt is made to move the manipulator arm manually over a desired programming path. Usually such prior art manipulators are programmed by selectively energizing driving motors in the different axes by means of push buttons on a so-called teach gun, the operator holding down one or more buttons until he visually determines that a desired position has been reached.
In order to be suitable for such portable ship-building applications, the drive motors must be light in weight and must also be capable of being accurately operable at very low speeds while still exhibiting high output torque to overcome the load of the manipulator arm due to gravity and forces from welding cables and associated equipment during playback. Further, the manipulator apparatus of the prior art does not have a geometrical design of the rotational axes and center of rotation to minimize loading forces on the drive system which is desirable in applications of manual programming.